Some economists are confident that they understand labor unions. Viewing unions as monopolies, they believe unions raise their members' wages by reducing labor supply to unionized trades. In this monopoly-union view, nonmembers pay for union wage gains through higher prices for union-made goods and lower wages for nonunion workers due to crowding into nonunion industries and trades. By tampering with the free-market distribution of labor, unions distort the fair distribution of wages and income and lower output by pushing workers from more- into less-efficient occupations.